Furnace wall arrangement



June 2, 1964 w. w. scHRoEDTER FURNACE WALL ARRANGEMENT 4 sheds-sheet 1 Filed July 27, 1961 INVENTOR Willburi W. Schroedter BY/La/bud/ ATTORNEY June 2, 1964 w. w. scr-IROEDTER 3,135,243

FURNACE WALL ARRANGEMENT Filed July 27, 1961 4 Sheets-Sheet 3 Fig. 4.

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lNvENToR wllburt w. Schroedter BY W MJ ATToRNEY w. w. scHRoEDTER 3,135,243

FURNACE WALL ARRANGEMENT June 2, 1964 4 Sheets-Sheet 4 Filed July 27 1961 INVENTOR Willburt W. Schroedter ATTORNEY United States Patent O 3,135,243 FURNACE WALL ARRANGEMENT Willburt W. Schroedter, West Hartford, Conn., assigner to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Y Filed July 27, 1961, Ser. No. 127,396 Claims. (Cl. 122-235) This invention relates generally to the art of vapor gen# eration and is particularly concerned with an improved vapor generator organization for operation at supercritical critical pressures and temperatures are such that natural circulation and separation of liquid and vapor as recognized in subcritical operation are either not possible or not satisfactory so Vthat supercritical vapor generators are of the forced once-through llow type wherein the feed pump forces the working medium through a continuous circuit from the inlet of the Vapor generator to its outlet with the feed being regulated in accordance with the output of the unit and with the working medium being heated to its desired temperature during passage through the unit, this medium being delivered at Athis desired temperature and the desired pressure to the point of use, as for example a turbine.

Since there is no heat of vaporization at and above supercritical pressure the temperature of the working medium progressively increases as it traverses through the once-through ilow system with each increment of heat imparted to the working medium resulting in a rise in temperature of the medium. T his effect necessarily poses a problem in connection with Welded panel walls in such a unit. This is so because the tubes which make up such a Wall will increase in temperature throughout their length and if the tubes are in parallel ,ow relation, adjacent tubes may vary significantly in temperature particularly toward the tube outlet as a result of variation in flow or variation in heat input.

Notwithstanding the problems connected with Welded panel wall type of construction, for economy, ease of fabrication and erection, as well as other various significant` purposes, it is extremely desirablerto be able to Aemploy this type of wall construction in these generators. This is particularly true in the furnace where it is desired to have these panels provide generally pressure-tight walls thereby simplifying fabrication, erection and support and yielding aconstruction which may be readily hung from its upper end and expand downwardly.

' In the forced once-through flow type of system, since Y the amount of working medium which flows through the system is dependent upon the actual load upon the vapor generator, this amount will vary as` the load changes. Accordingly, there is a minimum load at which the flow through the tubes is adequate to insure proper cooling thereof. This load is generally about 30 percent with this being considered a good working compromise in that the design can be reasonable and with adequateow at the 30 percent load the pressure drop at maximum load is still not intolerable.

The tubes that line the furnace wall are of particular concern with regard to overheating because of the high heat absorption rate of these tubes even at low load. Accordingly, various arrangements have been employed for lining the furnace Walls with tubes as for example, a

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number of parallel flow tubes have been extended up and down the furnace walls in ribbon fashion to form a tubular lining about the circumference of the furnace, with Patent No. 3,030,937, issued April 24, 1962, to E. C. Witzke disclosing this arrangement. Groups of riser panels have been positioned in side-by-side relation about the circumference of the furnace with each of the groups being connected at their lower ends with inlet headers and at their upper ends with outlet headers and with adjacent groups being connected in series ow relation, with this being known as the Benson construction.` In these arrangements the temperature variation between certain adjacent tubes on the furnace Wall is extremely high so as to make it extremely hazardous if not totally impracticable to provide a completely welded panel construction throughout the width of the wall. p

If, in lieu of the aforementioned types of wall construc- Vtion the walls of the furnace of the forced once-through flow supercritical vapor generator are lined with side-byside tubes, each adjacent one of which is in parallel flow relation and with the tubes along each wall being welded throughout the length of the wall into a panel, such an larrangement is subject to serious objections. Since the relationship between output of the unit and the circumference of the furnace that is required is fixed within definite limits a large number of parallel-How tubes are required to line the furnace so that even at a minimum 30% ow, as previously mentioned, these tubes must have an unusually small diameter of about 1'or smaller in order that the necessary average uid velocity will be provided through the tubes to insure adequate cooling of them. The restrictive .effect that deposits and tolerances in -the tubeshave upon tube temperature is substantially greater for these small diameter tubes than for tubes of larger diameter. Furthermore, if fins are employed on these relatively small diameter tubes there is presented an unfavorable area relationship of steel to fluid for heat transfer purposes. In addition these panels have a rather low flexibility to accommodate thermal displacements. Beyond these objections there is the very serious problem of non-uniform temperature distribution throughout such panels that line each of the walls.Y Tubes in different locations of thefurnace will be subjected to very different heat inputs or heat absorption so that across the walls of the furnace the tubes that make up the panels will receive varying amounts of heat. This is especially true for low loads and in particular under start-up conditions since at this time the ratio of furnace heat absorption to overall absorption is at its peak and the entering or feed water temperature is low. This requires, on the one hand, that measures be taken to increase stability within the tubes, such as orifices to control thepressure dropy through thetube, and, on the other hand, leads to considerable thermal stresses across the panel width. As a result of starting the unit and changing load on theyunit these stresses vary so that a cyclic stress condition is set up which is susceptiblerof causing fatigue failure over a period of time. 5

The variation of these stresses with changing load is caused among other things by variation of thetemperature difference between the inlet and the outlet ofthe tubes of the panels with varying load and variation of the heat absorption transversely of the furnace wall with varying load. The higher the temperature diercnce between inlet and outlet the greater the danger of there being a considerable outlet temperature unbalance across the panels and around the furnace circumference. VThe temperature difference between the inlet and outlet of each of the tubes is a result of the effect in a once-through flow supercritical generating system of the temperature pro'- 'gressively increasing throughout the through-now system. The heat absorption transversely ofthe furnace walls becomes less uniform as the iiring rate is decreased, so that temperature unbalance across the panels will become greater as the load is decreased. The temperature diiferental between inlet and outlet of the tubes of the panels also will increase as the load decreases. This is so, because, as previously mentioned, the ratio of furnace absorption to over-al1 absorption of the unit is at its peak at low load operation and the temperature of the water entering the panels is low. Thus the temperature differentials in the panels change with changing load causing cyclic development of stresses within the tube panels which present the danger of ultimate fatigue failure of the welded wall.

The present invention provides a once-through ow supercritical vapor generator having welded panel wall type construction and wherein the design of the tubular panel walls is not limited by requirements of the throughflow system and also wherein the stresses in these panel walls resulting from differential temperatures are maintained at a minimum. These advantageous results are achieved by superimposing a circulating system on the once-through flow system with this circulating system being in parallel with or connected across the panel walls and being effective to supplement the through-flow through the tubes that make up these walls. By supplementing the through-flow in the tubes that make up the panel walls, the temperature rise between the inlet and the outlet of the tubes, particularly during start-up and at low loads, ,is greatly reduced being only a fraction of the Value that it would be without the supplemental flow. This supplemental flow also reduces the possibility of unbalance of fluid temperature in the tubes across the panel and accordingly unbalance of the tube metal temperatures. This is so whether this unbalance iiuid temperature is caused by flow variation due to tube geometry or by uneven heat absorption.

f The reduction of temperature rise between inlet and outlet further improves the stability of ow between the heated parallel tubes, whichis principally a function of the properties of the fluid along the heated path. This increase in stability in turn reduces the possibility of temperature unbalances.

' In addition to providing a more uniform temperature distribution both longitudinally and transverselyfof the tubular panels this superimposed circulating system on the once-through ow system enables the designer to design the tubular panel walls in accordance with considera.- tions other than those dictated by the once-through flow system. The tube size may be selected for the one best 'suited for the requirements of the service. It will be suiciently large to avoid any substantial effect or influence by mill tolerance and deposits on pressure flow and temperature. The tube wall thickness can be selected on the basis of pressure and temperature considerationsl only. However in a panel wall construction in a supercritical through-how generator without the circulating system of the invention, the wall thickness of uniform outside diameter tubes may have to be increased, beyond that necessary for the temperature and pressure considera- ,tions in order to reduce the inside diameter and provide an area which will give the necessary iiow velocity through a critical portion ofthe tube. The circulating system of vthe invention permits the panel geometry, i.e. the relationship of outside diameter, wall thickness, spacing, 1in placement and size, to be selected so as to provide improved panel exibility as well as a surface pattern best suited to the furnace operation.

Thevpresent inventioncontemplates panel wall construction for both the furnace walls which delineate the furnace and a center partition wall which divides the furnace into two adjacent compartments with all of these walls being of tubular panels and with the partition wall .and the furnace walls being in series-ow relation with regard to flow of the working uid. This series-How relation of the panels has the effect of providing a de,-

4 creased temperature differential between the inlet and outlet of the tubes of the panels over that which would prevail if the center wall panel was in parallel flow relation with the furnace wall panels.

Accordingly, it is an object of the present invention to provide an improved once-through flow supercritical vapor generator.

A further object of the invention is to provide an improved once-through ow vapor generator operating at supercritical pressures and provided with tubular panel wall type construction in which the stresses within the panel walls are maintained at a relatively low value.

A still further object of the invention is to provide a once-through ilow vapor generator operating at supercritical pressures and having tubular panel wall type construction with ilexibility in the design of the panel walls being permitted and with this design not being restricted by requirements of the through-flow portion of the system. Y Still another object of the invention is to provide a once-through flow vapor generator operating at supercritical pressures and provided with a panel wall construction including a center partition wall and wherein the temperature differential between inlet and outlet of the furnace walls and the partition walls is maintained at a relatively low value.

Another object of the invention is to provide a oncethrough ilow vapor generator operating at supercritical pressures and provided with panel wall construction wherein the flow through the panel walls is not limited to that of the throughiiow but may be supplemented particularly as the load is decreased in order that stresses within the tubes resulting from differential temperatures may be maintained at a minimum and in order that the design of the panels may be the optimum.

Other features and advantages will be apparent from the speciiicataion and claims, and from the accompanying drawings which-illustrate a preferred embodiment of the invention, and in which:

FIGURE 1 is a vertical sectional View of a once-through ilow supercritical vapor generator embodying the present invention with this view being somewhat diagrammatic in nature; Y

FIGURE 2 is also a vertical sectional view somewhat diagrammatic in nature with this View being taken generally along line 2--2 of FIG. l;

FIGURE 3 is a transverse section taken generally along line 3 3 of FIG. 1; Y

FIGURE 4 is a skeletonized perspective View of the vapor generator of FIG. 1 showing how the various walls of the furnace are interconnected with the through-flow system and with the superimposed circulating system;

FIGURE 5 is a fragmentary sectional View through one of the side walls of the vapor generator;

FIGURE 6 is a sectional view of one of the side walls of the vapor generator with this section being taken generally along line 6 6 of FIG. 1; and

FIGURE 7 is an elevational view of a portion of one of the side Walls with this view being taken generally along line 77 of FIG. 6 and with this view showing how the spacing of the tubes is increased in order to provide tubular wall coverage for the lateral gas pass extending from the furnace outlet.

Considering now in detail the illustrative organization depicted in the drawing, the once-through tlow supercritical unit shown therein includes furnace 10 which is vertically disposed and has an outlet for combustion gases at its upper end and provided in its rear wall. Extending from this outlet is the lateral gas pass 12 which connects with the upper end of the vertically extending gas pass 14 that extends downwardly in parallel relation with the furnace. Combustion gases pass up through furnace 10, through the outlet and then through gas passes 12 and 14 with the gases being conveyed from this latter gas pass to a stack and traversing, as is conventional, a suitable air heateror other heat exchange equipment.

As illustratively disclosed furnace is iired by means of tangentially arranged burners16 which are disposed to provide a whirling gas mass in the two furnace compartments 18 and 20, FIG. 3. While tangential type of firing has been illustratively disclosed in the drawings other well known types of firing may be employed with the inventive organization as for example either the horizontal or vertical cyclone type firing may be used where crushed coal is burned in cyclone chambers or front-wall or opposed-wall firing may be employed. The so-called turbo ring may also be utilized wherein burners, horizontally arranged on opposite walls, are directed downwardly toward the furnace bottom. Regardless of the type of firing employed hot combustion gases are generated in the lower region of the furnace 10 and pass upwardly therethrough and out the outlet at the upper portion of the furnace.

The furnace is made up of front wall 22, rear wall 2d, and side walls 26. Centrally disposed between side walls 26 is partition wall 28 which extends between but termi nates, at least throughout a major portion of its length, in spaced relation with front and rear walls 22 and 24- with the'partition wall 28 dividing the furnace into the aforementioned compartments 18 and 26 which extend vertically throughout the heighth of the furnace.

The once-through flow system of the vapor` generator is comprised of a number of heat exchange portions or sections which are connected in series flow relation and through which the through-flow is forced by means of the feed pump. For convenience of identification thesey heat exchange sections may be identified as the economizer, the wall tube heating sections and the heating sections comprising tubular members extending down into the gas passageways and the furnace. Feed pump 30 forces the working medium through the economizer 32 which is comprised of numerous tubular elements in parallel flow relation and positioned generally at the lower end of gas pass 14. From economizer 32 the throughflow is conveyed through conduit 34 to mixing vessel 36 and from this mixing vessel the iiuid flows down through conduit 38 to the inlet header 40 positioned at the bottom of center wall or partition wall 28.

This partition wall 28 is comprised of vertically extending side-by-side tubular members 29 which are connected at their lower end with the header 40 and at their upper end with header 42. Alternate tubes of the center wall are bent at the lower end of the wall in order to form one side of the hopper bottom for each of the furnace compartments. Each adjacent tube in the center with is in elfect a separate tube that extends only lonce throughout the length of the center wall being connected at its upper and lower ends to the outlet and inlet headers of the wall respectively. The working medium ilows up simultaneously through all of the tubes of the center wall from header 4t) to header 42 in parallel flow relationship through the various tubes. V

From outlet header 42 the working medium is conveyed by downcomers 44 to the inletheader means designated generally 46 from which the iluid is distributed to the tubes which line the furnace'walls. This `header means includes the headers 48 to which are connected the lower ends of tubes 50 that are disposed in side-by-siderelation and extend vertically up along the side walls 26 connecting at their upper end with outlet headers 52. The header arrangement 46 also includes header 54 to` which the lower end of tubes 56 are connected with these tubes being in side-by-side relation and extending vertically up along front wall 22 being bent at their upper region to extend along the roof of the furnace and then conneet with outlet header 58. Also forming part of the header arrangement 46 is header 60 to which the lower ends of tubes 62 are connected with these tubes being disposed in`sidebyside relation and extending up along the rear wall 24 of the'furnace with some of these tubes 62 being bent to extend along and conform. with nose baille 64 while others continue their vertical extension across the back of theV nose baille with the tubes 24 extending'across gas pass 12 and connecting at their upper end with outlet header 58. The headers 52 are interconnected with header 58 so that the eluent from the wall tubes is all received inthe distribution header 66 which is connected with header 58 via a number of connecting conduits 63.

From the distributing header 66 the through llow` is conveyed to and through the group of sinuously bent tubes 7i) which are supplied from the distribution header 66 via conduit 72 header 76 and headers 71, FIG. l. The discharge from the tube group 70 is received in header 74 which is in turn connected with header 78. Connected with this latter header is the inlet of the tubes which make up the panel type heat exchange portion that extends down into the upper end of the furnace and is comprised of a plurality of panels disposed in side-by-side relation across the furnace. In traversing the panel heat exchange portion S0 the fluid is heated to its desired temperature and is at its desired supercritical pressure and accordingly is delivered to the turbine 82. j

As disclosed the unit is provided with a reheater 84 disposed in gas pass 12 and which is connected with the turbine S2 in the usual manner to reheat the vapor after it has given up a portion of its energy.

The exhaust from the turbine 82 is received in condenser 83 where the vapor is condensed and this condensate is pumped by pump 85 through feedwater heaters 87 and daerator S9 to the inletof feed pump 30.

Each of the side-by-side tubes that line the inner surface of the furnace walls 22, 24 and 26 are in effect separate tubes which extend between the inlet and outlet headers of the respective walls with each adjacent tube being in parallel flow relation so that all of the tubes lining the furnace walls are in parallel ilow relation with the through-flow passing upwardly through these parallel ilow paths. Adjacent tubes on each wall are welded together throughout the length of the wall with the juncture of the tubes being shown in FIG. 5. As illustratively disclosed in FIG. 5, tubes 50 are joined together throughout the length of the wall by providing spacer 86 between each adjacent pair of tubes and welding this spacer to the tubes throughout the wall length.

At the 4upper region ofthe funrace a number of the tubes on each side wall and which are nearest rear wall 24 are bent, as disclosed in FIG. 7, so that their spacing is increased. This is done in order that a tubular lining may be provided for a portion of the side walls of gas pass l2 as well as the side walls of the furnace. The spacer 86' between these more widely spaced tube portions on` the side walls of gas pass 12 have a greater width thanthe previously mentioned spaces 86, however, they are still welded to the tubes throughout their overlying length in order to provide a generally imperforate structure.

By welding adjacent tubes along each of the furnace walls throughout the length of the furnace wall a generally imperforatel gas tight tubular inner casing or lining is formed which simplifies wall construction and goes a long way towards providing a pressure resistant gastight furnace. Furthermore it is preferred to weld adjoining panels together at the corners of the furnace and throughout the panel height so that longitudinally extending seals may be omitted for the furnace and so the inner tubular wall construction provides a complete, gastight encasement. The center wall is also preferably of welded construction in order to provide greater strength and in orderV to provide a surface to which slag is much less likely to adhere. As previously mentioned, the center wall throughout a major portion of its length terminates in spaced relation with the front and rear walls of the furnace in order to provide a suitable opening or passage between the compartments 1S and 20 for pres.- sure equalization and other purposes.

7 In order that the through-flow both the center partition wall and the furnace walls may be supplemented to n thereby overcome the very serious objections which other- Wise prevail with such a welded furnace Wall construction in a once-through supercritical unit there is provided a circulating system superimposed on the throughow system for recirculating a portion of the Working fluid through the tubes that make up these wall portions. This circulating system includes conduit 88 which is connected with distribution header 66 that receives the working medium egressing from the tubes extending up along the furnace walls. This conduit 88 is connected with pump 90 which has its outlet connected with mixing vessel 36. Accordingly, through this circulating system, which is effectively connected in bypass relation or across the combined center wall and furnace wall heat exchange portions, a portion of the working medium .may be reintroduced into and be circulated through these heat exchange portions. Therefore the fluid ow through the tubes which make up the center partition wall and the furnace walls may be supplemented with respect to the through-How and accordingly is not restricted to the through-flow.

The unit may be designed so that in its upper load range no recirculation is necessary since in this range the through-flow is sufficiently great to provide ample velocity through the center wall and furnace wall tubes without encountering the objections hereinbefore mentioned. However, as the load is decreased on the unit and the throughflow accordingly decreased it is necessary to supplement the through-How through the center partition wall and the furnace wall tubes and accordingly as the load decreases the circulating system is effective to circulate the working medium or a portion of the working medium through y these portions of the through-flow system.

As an illustrative example the circulating pump 9) may be a constant speed pump and may be so designed that at 70 percent load it become effective to initiate circulation through the center partition wall and the furnace wall tubes. As the load on the unit decreases this constant speed pump will be effective to maintain the velocity through the center partition wall and furnace wall tubes adequate to insure against tube failure and of course as the load decreases the pump will be effective to circulate a greater proportion of the total flow through the center partition and furnace wall tubes.

In the connection between the pump 90 and the mixing vessel 36 there is preferably provided a check valve 92 to prevent reverse flow through the pump and conduit 88.

Center partition wall 28 and the furnace walls are connected in series flow relation in order to decrease the differential temperature between the inlet and the outlet of the tubes making up these wall portions. Whether these wall portions are connected in parallel or in series ow relation the amount of heat that must be absorbed by the fluid owing through them would have to be the same, since this would be a requirement in order to meet the load imposed upon the vapor generator. It is accordingly apparent that the difference in temperature in the working medium entering and leaving these wall portions Will be substantially less if they are connected in series than if they are connected in parallel. This becomes obvious when it is considered that when connected in series the heating of the working uid from its initial temperature upon entering the center wall to its iinal temperature upon leaving the furnace walls is accomplished in two stages while with a parallel flow arrangement this temperature increase would be elfected in a single stage. The total flow area of the tubes 29 of the center wall is substantially less than the total combined ilow area of the outer furnace wall tubes 50, 56 and 62. This is necessary in order that the center wall tubes may be maintained an acceptable size and not become inordinately large. As an illustration of the tube sizes the center wall tubes may be 2" O.D. and the furnace wall tubes 11/2" O.D. This gives the center wall about one-quarter the flow area of the outer furnace walls.v This smaller flow area has the advantage of providing a greater flow velocity through the tubes and accordinglymore adequate cooling. Furthermore it is preferred to have the center wall be upstream of the outer furnace walls relativeto the flow of the working medium and with relation to the furnace Walls. This is no because the iluid then tlowing through the center wall will have a lower specific volume (giving a lower pressure drop) and a lower temperature than that liowing through the furnace walls. Since the center partition wall is subjected to heat on both sides and accordingly has more severe operating conditions it is of advantage to have the lower temperature fluid flowing through the tubes of the center partition wall. Since the tube size of the center wall must necessarily be limited, the lower specific volume encountered with this arrangement is extremely important.

lt is the superimposing of the circulating system on the once-through flow system of the supercritical vapor generator and in particular on the welded panel wall portion of the once-through flow system whichl permits the use of this panel construction while maintaining relatively low stresses due to temperature differences transversely of the panel walls and particularly the cyclic stresses caused by temperature changes resulting from change in load and which are otherwise of substantial magnitude particularly at low loads and start up. By providing a recirculation through the welded tubular wall panels in supplement to `the once-through flow through these panels the temperature dierential between the inlet and thc outlet of the tubes of the panels is greatly decreased giving much greater stability. This is so because the portion of the medium that is recirculated is substantially higher in temperature than the through-flow medium that enters the tubular panels. By mixing this recirculated portion with the through-flow portion in mixing vessel 36 the temperature of the medium entering the panels is substantially increased. The recirculation provides for less unbalance since the tubes of the panel may be of larger diameter than they could be without the recirculation so that the tubes may be sized so the effect of deposits and mill tolerance may be greatly reduced and made unsubstantial, which contributes to balance of flow through the tubes. By thus providing for a stable and balance flow through the tubes of the center partition wall and the tubes of the furnace wall each of the tubes will have a more uniform temperature gradient throughout their length and a more uniform temperature transversely of the welded tubular panel. Long term fatigue failure is accordingly minimized.

Since all of the tubes that make up the panels on the furnace walls are in parallel flow relation they will all generally be at the same temperature so that the furnace may be hung from above and will expand vertically downward. For this purpose hanger rods 93 may be provided which extend down from structural steel members, as shown (FIG. 1), and are connected with some of the tubes on each wall. The welded tubular panel wall type of construction greatly simplifies support of the unit and construction of the furnace walls permitting a known and proven outer wall design, including buckstays and their supports to be employed.

Accordingly it will be seen that by means of the present invention there is provided a once-through ow vapor generator designed to operate at supercritical pressures and which is provided with a novel organization which enables the tubular panel wall type construction to be employed while providing for freedom of design with regard to the tubular panels and maintaining the stresses developed within the panels during operation at a minimum, and further by arranging the center wall in series with outside furnace walls, the temperature gradients are approximately halved and the stress and fatigue possibilities greatly reduced. In addition by placing the center Wall ow It is to be understood that the invention is not limited to the specific embodimentherein illustrated and described, but may be used in other Ways without departure from its spirit, and that various changes can be made which would come within the scope of the invention which is limited only by the appended claims.

I claim:

l. A vapor generator of the once-through flow type for operation at supercritical pressure and having a throughflow system through which the working medium is forced, said generator including a furnace defined by elongated wall members that are lined with separate tubes in sideby-side relation across said members and extending longitudinally thereof to absorb heatfrom Within the furnace and which is produced as a result of the burning of a fuel, these tubes being in parallel flow relation with respect to the working medium and forming part of the through-flow system of the generator, the tubes being integrally bonded together generally throughout the length of their respective Walls, a partition Wall disposed Within and extending longitudinally of the furnace, said partition wall being comprised of separate longitudinally extending tubes in side-by-side relation across the Wall and in parallel ow relation, said partition wall tubes also forming part of the through-flow system of the generator, but being in series lio-W relation with the furnace wall tubes with the total ow area of the partition wall tubes being substantially less than that of the furnace Wall tubes in parallel flow relation, and means for increasing the flow of the working medium through the furnace wall tubes and the partition wall tubes with the total flow area of the partition wall tubes being substantially less than that of the furnace wall tubes in parallel liow relation above that of the through-flow including a circulating system superimposed on the through-flow system and effective to recirculate a portion of the Working medium after traversal of the tubes of the center wall and furnace walls back therethrough.

2. A vapor generator of the once-through ow type for operation at supercritical pressure and having a through-How system through which the Working medium is forced, said generator including a vertically disposed furnace, means for firing a fuel and generating combustion gases that pass through the furnace with the furnace lbeing provided with an outlet remote from this last mentioned means, said furnace being defined by vertically elongated wall members which are lined with separate, generally vertically extending tubes in side-by-side relation across the width of each wall member, said tubes being in parallel flow relation and with adjacent tubes on each wall being bonded together generally throughout the height of the Wall, forming part of said through-flow system, a vertically disposed partition Wall effectively partitioning the furnace and comprised of separate, vertical tubes in side-by-side relation across the width thereof,

`said partition wall forming part of said through-How system with the tubes of the partition wall being in parallel ow relationl relative to each other but in series fiow relation with the furnace wall tubes, said furnace wal-1 tubes and partition wall tubes being connected into the throughow system so that the through-flow is upwardly therethrough, and a circulating system superimposed on the through-flow system in parallel relation with the partition wall and the furnace Wall tubes and effective to recirculate working medium through these portions of the through-flow system in supplement to the through-flow.

3. A vapor generator of the once-through How type for operation at supercritical pressure and having a through-how system through which the working medium is forced, said generator including a vertically disposed furnace, means for ring a fuel and generating combustion gases that pass through the furnace with the furnace being provided with an outlet remote from this last men` tioned means, said furnace being defined by vertically elongated wall members which are lined With separate,

generally vertically extending tubees in side-by-side relation across the width of each wall member, said tubes being in parallel flow relation and connected into said through-ow system so the through-flowof working medium is upwardly therethrough with adjacent tubes on each wall being bonded together throughout the height of the Wall, inlet header means for said wall tubes at the lower end of the furnace and outlet header means at the upper end, a vertically disposedpartition wall extending longitudinally within the furnace and comprised of vertically extending tubes connected at their lower end with inlet header means and at the outlet upper end with outlet header means, said partition Wall connected into said through-flow system so the working medium flows upwardly therethrough, means conveying the through-flow egressing from the partition wall tubes to the inlet header means' of the furnace wall tubes, conduit means superimposed on the once-through system in by-pass relation with the partition wall and the furnace wall tubes connected to receive a portion of the working medium after it has passed through the partition wall and furnace wall tubes and introduce the same for repassage through these heat exchange portions, and pump means `for effecting such flow of the Working medium.

4. In a forced through-flow supercritical vapor generator, a forced through-flow circuit through which the working medium is conveyed, a furnace having parallel flow tubes on its walls forming part of the' through-flow system, and a furnace partition wall comprised of parallel flow tubes also forming part of the through-flow systern, in series with and upstream of said furnace Wall tubesV relative to flow of the working medium through the through-flow circuit.

5. A forced through-flow supercritical vapor generator including a tubular forced through-flow circuit through which the Working medium is conveyed, a furnace having its Walls lined with parallel flow tubes, a furnace partition wall comprised of parallel ow tubes and effectively compartmenting the furnace, the total flow area of the partition Wall tubes being substantially less than that of the furnace wall tubes in parallel flow relation, said partition wall tubes and said furnace Wall tubes forming part of the through-How system with the partition Wall tubes being upstream of the furnace wall tubes.

6. A forced through-flow supercritical vapor generator including a tubular forced through-now circuit through which the working medium is conveyed, a vertically disposed furnace having its walls lined with vertically extending tubes in side-by-side relation throughout the wall perimeter and in parallel flow relation, a vertically disposed partion wall in said furnace comprised of vertical, side-by-side tubes also in parallel flow relation and having a total flow area substantially less than that of said parallel ow Wall tubes, these partition wall and furnace wall tubes forming part of the through-flow system, said system including means to direct the through-flow up through the center wall tubes and thereafter up through the furnace wall tubes.

7. A forced through-flow supercritical vapor generator including a tubular forced through-flow circuit through which the working medium is conveyed, an

elongated furnace defined by wall members which are` of longitudinally extending tubes in parallel iiow relation and forming part of the through-flow system, said partition wall tubes. being in series flow relation with the furnace Wall tubes and upstream thereof with relation to flow of the Working medium, and a circulating system l 1 superimposed on the through-how system and operative toV circulate the working medium through the partition wall and furnace wall portions of said system. f

8. A forced through-flow supercritical vapor generator including a tubular forced through-How circuit through which the working medium Vis conveyed, said generator including a vertically disposed furnace, means for firing a fuel and generating combustion gases that ow through the furnace from the lower regi'on upward with the furnace having a lateral outlet at its upper region, gas passageway means extending from said outlet including a portion extending down alongside said furnace being dencd by vertically elongated wall members which arel lined with separate, generally vertically'extending tubes in side-by-side relation across the width of each wall member, said tubes being in parallel flow relation relative to the working medium yand connected into said through-` ow system so the through-flow of working medium is upwardly therethrough with adjacent tubes on each wall being bonded together throughout the height of the wall, means for supporting said tubular walls from above for expansion downward,` a partition wall within said furnace and extending vertically thereof,`said partition wall being comprised of side-by-side vertically extending tubes in parallel ow relation with the flow area of the partition wall tubes being substantially less than that of the furnace wall tubes in parallel flow relation means effective to reduce the temperature gradient transversely of the tubular partition and furnace walls and longitudinally thereof comprising a circulating system superimposed on the through-flow circuit and operative to provide a flow of` working medium through the tubes of these walls in supplement to the through-dow, the through-flow system also including a heat exchange bundle upstream of the partition wall and furnace wall tubes and disposed` in the lower region of said gas passageway means and also tubular panelsextending into the upper furnace region and connected into the through-How circuit downstream of the Wall tubes.

' 9. In a forced through-flow supercritical vapor generator, a forced through-flow circuit through which the working medium is conveyed, a furnace having parallel flow tubes on its walls forming part of the through-flow system, and a furnace partition wall comprised of parallel flow tubes also forming party of the through-flow system, in series with and upstream of said furnace wall tubes relative to the ow of the working medium through the through-flow circuit, said furnace wall tubes being bonded together throughout the extent of the furnace and means operative to provide a flow through said furnace wall tubes greater than the through-flow.

10. In a forced through-flow supercritical vapor generator, a forced through-flow circuit through which the working medium is conveyed, a furnace having parallel flow tubes on its walls forming part of the through-flow system,'and a furnace partition wall comprised of parallel flow tubes with the total How area of the partition wall tubes being substantially less than that of the furnace wall tubes in parallel ow relation, said partition wall tubes also forming part of the through-how system and connected in series flow relation with, and upstream of the furnace wall tubes, said furnace wall tubes bonded together throughout the extent of the furnace and means operative to provide a flow through said furnace wall tubes greater than the through-flow.

References Cited in the tile of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N O. 3,135 243 y June Z 1964 Wllburt W. Schroedter It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, line 8, for "no" read so column 9, 33 to 35, strike out "with the total flow area of the partition wall tubes being substantially less than that'of the furnace wallv tubes in parallel flow relation" and insert thev same after "tubes," in line 6l, same column 9; column ll, line l2, after "furnace" insert said furnace Signed andv sealed this 13th day of October 1964.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents 

9. IN A FORCED THROUGH-FLOW SUPERCRITICAL VAPOR GENERATOR, A FORCED THROUGH-FLOW CIRCUIT THROUGH WHICH THE WORKING MEDIUM IS CONVEYED, A FURNACE HAVING PARALLEL FLOW TUBES ON ITS WALLS FORMING PART OF THE THROUGH-FLOW SYSTEM, AND A FURNACE PARTITION WALL COMPRISED OF PARALLEL FLOW TUBES ALSO FORMING PART OF THE THROUGH-FLOW SYSTEM, IN SERIES WITH AND UPSTREAM OF SAID FURNACE WALL TUBES RELATIVE TO THE FLOW OF THE WORKING MEDIUM THROUGH THE THROUGH-FLOW CIRCUIT, SAID FURNACE WALL TUBES BEING BONDED TOGETHER THROUGHOUT THE EXTENT OF THE FURNACE AND MEANS OPERATIVE TO PROVIDE A FLOW THROUGH SAID FURNACE WALL TUBES GREATER THAN THE THROUGH-FLOW 